This invention relates generally to the field of telecommunications, and more particularly to a synchronous switch and method for a telecommunications node.
The Internet has dramatically increased the potential for data, voice, and video services for customers. Existing circuit-switched telephony systems, however, do not provide the foundation to support the growing need for bandwidth and new services required by both residential and business consumers. As a result, integrated access devices have been introduced to support Internet and related technologies as well as standard telephony service for customers.
Integrated access devices often combine synchronous and asynchronous transport and switch functionality to multiplex data, voice, and video traffic together onto a single network. Within an integrated access device, a time division multiplex (TDM) bus is typically used to transport voice and other synchronous traffic between the line cards and a switch core. An asynchronous transfer mode (ATM) bus is used to transport ATM traffic between the line cards and the switch core.
At the switch core, ATM traffic normally arrives asynchronously while TDM traffic arrives in a regular and periodic fashion. Separate ATM and TDM switch hardware are provided at the switch core to receive and process the ATM and TDM traffic, respectively. TDM traffic may be segmented to and reassembled from the ATM format using ATM adaption layer (AAL) standards for high-speed transmission on the network and for distribution to customer premises after transmission over the network. The separate data paths and switching hardware for ATM and TDM traffic is expensive and may be cost prohibitive for some lower rate applications.
The present invention provides a synchronous switch and a method for a telecommunications node that substantially reduces or eliminates the disadvantages and problems associated with previous systems and methods. In particular, the synchronous switch uses a common data path and memory to switch both asynchronous transfer mode (ATM) and time division multiplex (TDM) traffic. As a result, switching hardware is reduced and line cards communicating with the synchronous switch may include a mix of both ATM and TDM traffic.
In accordance with one embodiment of the present invention, a synchronous switch for a telecommunications node includes a switch interface operable to terminate a bus and to receive from the bus a frame having a plurality of time slots. The time slots are each operable to transport a traffic cell. A switch controller is operable to determine a type for each traffic cell received at the switch interface and to determine based on the type for a traffic cell an address for storing the traffic cell in a switch memory. The switch memory is operable to receive the traffic cell from the switch interface and the address for storing the traffic cell from the switch controller and to store the traffic cell at the address.
More particularly, in accordance with a particular embodiment of the present invention, the switch memory includes a plurality of TDM memory slots in a plurality of ATM queues associated with output ports. In this and other embodiments, the switch interface is operable to extract a header for the traffic cell from a time slot transporting the traffic cell and to provide the header to the switch controller. The switch controller is operable to determine an address of an ATM queue in the switch memory for storing the traffic cell in response to determining from the header that the traffic cell is of an ATM type and to determine an address in a TDM memory slot in the switch memory for storing the traffic cell in response to determining from the header that the traffic cell is of a TDM type.
Technical advantages of the present invention include providing an improved switch for a telecommunications node. In particular, the switch receives both ATM and TDM traffic cells in time slots and utilizes a common data path and memory to perform cell switching. For TDM cells, the switch data path is configured to route the cell into a TDM memory slot that is accessed in a TDM manner. For ATM cells, the switch data path is configured to route the cells to queues associated with output ports for the cells. The dual functionality of the switch data path reduces switching hardware in the switch core. As a result, the cost of the switch core and the network element are reduced.
Another technical advantage of the present invention includes providing a synchronous cell-based switch for a telecommunications node. In particular, the switch operates synchronously at a defined frame pulse to switch ATM and TDM traffic cells. As a result, ATM adaption layer (AAL) cells transporting TDM traffic are switched synchronously at the cell level.
Other technical advantages of the present invention will be readily apparent to one skilled in the art from the following figures, description, and claims.